Detecting circuit for IEEE 1394 device

Abstract

An IEEE 1394 device detecting circuit includes a south bridge chip, a control device, an IEEE 1394 interface, and a resistor. The control device includes a power reset pin, a bus reset pin, and a cable power pin. The control device is connected to the south bridge chip through the bus reset pin, which is further connected to the power reset pin. The cable power pin is connected to a direct current power through the resistor. The control device is further connected to the IEEE 1394 interface, which is connected to an IEEE 1394 device.

1. An IEEE 1394 device detecting circuit, comprising:
 a south bridge chip; 
 a resistor; 
 a control device comprising a bus reset pin connected to the south bridge chip, a power reset pin connected to the bus reset pin, and a cable power pin connected to a power supply through the resistor; and 
 an IEEE 1394 interface connected to the control device. 
 
   
   
     2. The IEEE 1394 device detecting circuit as claimed in  claim 1 , wherein the resistance of the resistor ranges from 370 kΩ to 410 kΩ. 
   
   
     3. The IEEE 1394 device detecting circuit as claimed in  claim 1 , wherein the resistance of the resistor is about 390 kΩ. 
   
   
     4. A detecting method for IEEE 1394 device, comprising:
 inserting an IEEE 1394 device into a computer through an IEEE 1394 interface; 
 transmitting a signal to a control device from the IEEE 1394 interface; 
 resetting a bus reset pin and a power reset pin of the control device according to a logic level of the signal; 
 activating the control device; and 
 transmitting the signal by the control device to a south bridge chip. 
 
   
   
     5. The detecting method for IEEE 1394 device as claimed in  claim 4 , wherein the elapsed time between the inserting step and the resetting step is less than a predetermined value. 
   
   
     6. The detecting method for IEEE 1394 device as claimed in  claim 5 , wherein the predetermined value is 2 milliseconds.